1
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Deniaud A, Kabasakal BV, Bufton JC, Schaffitzel C. Sample Preparation for Electron Cryo-Microscopy of Macromolecular Machines. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 3234:173-190. [PMID: 38507207 DOI: 10.1007/978-3-031-52193-5_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/22/2024]
Abstract
High-resolution structure determination by electron cryo-microscopy underwent a step change in recent years. This now allows study of challenging samples which previously were inaccessible for structure determination, including membrane proteins. These developments shift the focus in the field to the next bottlenecks which are high-quality sample preparations. While the amounts of sample required for cryo-EM are relatively small, sample quality is the key challenge. Sample quality is influenced by the stability of complexes which depends on buffer composition, inherent flexibility of the sample, and the method of solubilization from the membrane for membrane proteins. It further depends on the choice of sample support, grid pre-treatment and cryo-grid freezing protocol. Here, we discuss various widely applicable approaches to improve sample quality for structural analysis by cryo-EM.
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Affiliation(s)
- Aurélien Deniaud
- Univ. Grenoble Alpes, CNRS, CEA, IRIG - Laboratoire de Chimie et Biologie des Métaux, Grenoble, France
| | - Burak V Kabasakal
- School of Biochemistry, University of Bristol, Bristol, UK
- Turkish Accelerator and Radiation Laboratory, Gölbaşı, Ankara, Türkiye
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2
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Zhang Y, Gan Y, Zhao W, Zhang X, Zhao Y, Xie H, Yang J. Membrane Protein Structures in Native Cellular Membranes Revealed by Solid-State NMR Spectroscopy. JACS AU 2023; 3:3412-3423. [PMID: 38155644 PMCID: PMC10751765 DOI: 10.1021/jacsau.3c00564] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/24/2023] [Revised: 11/08/2023] [Accepted: 11/09/2023] [Indexed: 12/30/2023]
Abstract
The structural characterization of membrane proteins within the cellular membrane environment is critical for understanding the molecular mechanism in their native functional context. However, conducting residue site-specific structural analysis of membrane proteins in native membranes by solid-state NMR faces challenges due to poor spectral sensitivity and serious interference from background protein signals. In this study, we present a new protocol that combines various strategies for cellular membrane sample preparations, enabling us to reveal the secondary structure of the mechanosensitive channel of large conductance from Methanosarcina acetivorans (MaMscL) in Escherichia coli inner membranes. Our findings demonstrate the feasibility of achieving complete resonance assignments and the potential for determining the 3D structures of membrane proteins within cellular membranes. We find that the use of the BL21(DE3) strain in this protocol is crucial for effectively suppressing background protein labeling without compromising the sensitivity of the target protein. Furthermore, our data reveal that the structures of different proteins exhibit varying degrees of sensitivity to the membrane environment. These results underscore the significance of studying membrane proteins within their native cellular membranes when performing structural characterizations. Overall, this study opens up a new avenue for achieving the atomic-resolution structural characterization of membrane proteins within their native cellular membranes, providing valuable insights into the nativeness of membrane proteins.
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Affiliation(s)
- Yan Zhang
- National
Center for Magnetic Resonance in Wuhan, State Key Laboratory of Magnetic
Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics
and Mathematics, Wuhan National Laboratory for Optoelectronics, Innovation Academy for Precision Measurement Science
and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
- University
of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Yuefang Gan
- National
Center for Magnetic Resonance in Wuhan, State Key Laboratory of Magnetic
Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics
and Mathematics, Wuhan National Laboratory for Optoelectronics, Innovation Academy for Precision Measurement Science
and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
- University
of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Weijing Zhao
- National
Center for Magnetic Resonance in Wuhan, State Key Laboratory of Magnetic
Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics
and Mathematics, Wuhan National Laboratory for Optoelectronics, Innovation Academy for Precision Measurement Science
and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
| | - Xuning Zhang
- National
Center for Magnetic Resonance in Wuhan, State Key Laboratory of Magnetic
Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics
and Mathematics, Wuhan National Laboratory for Optoelectronics, Innovation Academy for Precision Measurement Science
and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
| | - Yongxiang Zhao
- National
Center for Magnetic Resonance in Wuhan, State Key Laboratory of Magnetic
Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics
and Mathematics, Wuhan National Laboratory for Optoelectronics, Innovation Academy for Precision Measurement Science
and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
| | - Huayong Xie
- National
Center for Magnetic Resonance in Wuhan, State Key Laboratory of Magnetic
Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics
and Mathematics, Wuhan National Laboratory for Optoelectronics, Innovation Academy for Precision Measurement Science
and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
| | - Jun Yang
- National
Center for Magnetic Resonance in Wuhan, State Key Laboratory of Magnetic
Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics
and Mathematics, Wuhan National Laboratory for Optoelectronics, Innovation Academy for Precision Measurement Science
and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
- Interdisciplinary
Institute of NMR and Molecular Sciences, School of Chemistry and Chemical
Engineering, The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, P. R. China
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3
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Xie H, Zhao Y, Zhao W, Chen Y, Liu M, Yang J. Solid-state NMR structure determination of a membrane protein in E. coli cellular inner membrane. SCIENCE ADVANCES 2023; 9:eadh4168. [PMID: 37910616 PMCID: PMC10619923 DOI: 10.1126/sciadv.adh4168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 09/27/2023] [Indexed: 11/03/2023]
Abstract
Structure determination of membrane proteins in native cellular membranes is critical to precisely reveal their structures in physiological conditions. However, it remains challenging for solid-state nuclear magnetic resonance (ssNMR) due to the low sensitivity and high complexity of ssNMR spectra of cellular membranes. Here, we present the structure determination of aquaporin Z (AqpZ) by ssNMR in Escherichia coli inner membranes. To enhance the signal sensitivity of AqpZ, we optimized protein overexpression and removed outer membrane components. To suppress the interference of background proteins, we used a "dual-media" expression approach and antibiotic treatment. Using 1017 distance restraints obtained from two-dimensional 13C-13C spectra based on the complete chemical shift assignments, the 1.7-Å ssNMR structure of AqpZ is determined in E. coli inner membranes. This cellular ssNMR structure determination paves the way for analyzing the atomic structural details for membrane proteins in native cellular membranes.
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Affiliation(s)
- Huayong Xie
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
| | - Yongxiang Zhao
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
| | - Weijing Zhao
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
| | - Yanke Chen
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
| | - Maili Liu
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, P.R. China
| | - Jun Yang
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, P.R. China
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4
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Iudin A, Korir PK, Somasundharam S, Weyand S, Cattavitello C, Fonseca N, Salih O, Kleywegt GJ, Patwardhan A. EMPIAR: the Electron Microscopy Public Image Archive. Nucleic Acids Res 2023; 51:D1503-D1511. [PMID: 36440762 PMCID: PMC9825465 DOI: 10.1093/nar/gkac1062] [Citation(s) in RCA: 52] [Impact Index Per Article: 52.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 10/21/2022] [Accepted: 10/25/2022] [Indexed: 11/29/2022] Open
Abstract
Public archiving in structural biology is well established with the Protein Data Bank (PDB; wwPDB.org) catering for atomic models and the Electron Microscopy Data Bank (EMDB; emdb-empiar.org) for 3D reconstructions from cryo-EM experiments. Even before the recent rapid growth in cryo-EM, there was an expressed community need for a public archive of image data from cryo-EM experiments for validation, software development, testing and training. Concomitantly, the proliferation of 3D imaging techniques for cells, tissues and organisms using volume EM (vEM) and X-ray tomography (XT) led to calls from these communities to publicly archive such data as well. EMPIAR (empiar.org) was developed as a public archive for raw cryo-EM image data and for 3D reconstructions from vEM and XT experiments and now comprises over a thousand entries totalling over 2 petabytes of data. EMPIAR resources include a deposition system, entry pages, facilities to search, visualize and download datasets, and a REST API for programmatic access to entry metadata. The success of EMPIAR also poses significant challenges for the future in dealing with the very fast growth in the volume of data and in enhancing its reusability.
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Affiliation(s)
- Andrii Iudin
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Wellcome Genome Campus, Hinxton, Cambridgeshire, CB10 1SD, UK
| | - Paul K Korir
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Wellcome Genome Campus, Hinxton, Cambridgeshire, CB10 1SD, UK
| | - Sriram Somasundharam
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Wellcome Genome Campus, Hinxton, Cambridgeshire, CB10 1SD, UK
| | - Simone Weyand
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Wellcome Genome Campus, Hinxton, Cambridgeshire, CB10 1SD, UK
| | - Cesare Cattavitello
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Wellcome Genome Campus, Hinxton, Cambridgeshire, CB10 1SD, UK
| | - Neli Fonseca
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Wellcome Genome Campus, Hinxton, Cambridgeshire, CB10 1SD, UK
| | - Osman Salih
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Wellcome Genome Campus, Hinxton, Cambridgeshire, CB10 1SD, UK
| | - Gerard J Kleywegt
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Wellcome Genome Campus, Hinxton, Cambridgeshire, CB10 1SD, UK
| | - Ardan Patwardhan
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Wellcome Genome Campus, Hinxton, Cambridgeshire, CB10 1SD, UK
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5
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Structure of cell-cell adhesion mediated by the Down syndrome cell adhesion molecule. Proc Natl Acad Sci U S A 2021; 118:2022442118. [PMID: 34531300 DOI: 10.1073/pnas.2022442118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/09/2021] [Indexed: 11/18/2022] Open
Abstract
The Down syndrome cell adhesion molecule (DSCAM) belongs to the immunoglobulin superfamily (IgSF) and plays important roles in neural development. It has a large ectodomain, including 10 Ig-like domains and 6 fibronectin III (FnIII) domains. Previous data have shown that DSCAM can mediate cell adhesion by forming homophilic dimers between cells and contributes to self-avoidance of neurites or neuronal tiling, which is important for neural network formation. However, the organization and assembly of DSCAM at cell adhesion interfaces has not been fully understood. Here we combine electron microscopy and other biophysical methods to characterize the structure of the DSCAM-mediated cell adhesion and generate three-dimensional views of the adhesion interfaces of DSCAM by electron tomography. The results show that mouse DSCAM forms a regular pattern at the adhesion interfaces. The Ig-like domains contribute to both trans homophilic interactions and cis assembly of the pattern, and the FnIII domains are crucial for the cis pattern formation as well as the interaction with the cell membrane. By contrast, no obvious assembly pattern is observed at the adhesion interfaces mediated by mouse DSCAML1 or Drosophila DSCAMs, suggesting the different structural roles and mechanisms of DSCAMs in mediating cell adhesion and neural network formation.
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6
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The journey of herpesvirus capsids and genomes to the host cell nucleus. Curr Opin Virol 2021; 50:147-158. [PMID: 34464845 DOI: 10.1016/j.coviro.2021.08.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 08/06/2021] [Accepted: 08/09/2021] [Indexed: 01/04/2023]
Abstract
Starting a herpesviral infection is a steeplechase across membranes, cytosol, and nuclear envelopes and against antiviral defence mechanisms. Here, we highlight recent insights on capsid stabilization at the portals during assembly, early capsid-host interactions ensuring nuclear targeting of incoming capsids, and genome uncoating. After fusion with a host membrane, incoming capsids recruit microtubule motors for traveling to the centrosome, and by unknown mechanisms get forward towards the nucleus. The interaction of capsid-associated tegument proteins with nucleoporins orients the capsid portal towards the nuclear pore, and presumably after removal of the portal caps the genomes that have been packaged under pressure can be injected into the nucleoplasm for transcription and replication. Some cell types disarm the incoming capsids or silence the incoming genomes to reduce the likelihood of infection.
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7
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Yang JE, Larson MR, Sibert BS, Shrum S, Wright ER. CorRelator: Interactive software for real-time high precision cryo-correlative light and electron microscopy. J Struct Biol 2021; 213:107709. [PMID: 33610654 PMCID: PMC8601405 DOI: 10.1016/j.jsb.2021.107709] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 01/06/2021] [Accepted: 02/11/2021] [Indexed: 12/31/2022]
Abstract
Cryo-correlative light and electron microscopy (CLEM) is a technique that uses the spatiotemporal cues from fluorescence light microscopy (FLM) to investigate the high-resolution ultrastructure of biological samples by cryo-electron microscopy (cryo-EM). Cryo-CLEM provides advantages for identifying and distinguishing fluorescently labeled proteins, macromolecular complexes, and organelles from the cellular environment. Challenges remain on how correlation workflows and software tools are implemented on different microscope platforms to support automated cryo-EM data acquisition. Here, we present CorRelator: an open-source desktop application that bridges between cryo-FLM and real-time cryo-EM/ET automated data collection. CorRelator implements a pixel-coordinate-to-stage-position transformation for flexible, high accuracy on-the-fly and post-acquisition correlation. CorRelator can be integrated into cryo-CLEM workflows and easily adapted to standard fluorescence and transmission electron microscope (TEM) system configurations. CorRelator was benchmarked under live-cell and cryogenic conditions using several FLM and TEM instruments, demonstrating that CorRelator reliably supports real-time, automated correlative cryo-EM/ET acquisition, through a combination of software-aided and interactive alignment. CorRelator is a cross-platform software package featuring an intuitive Graphical User Interface (GUI) that guides the user through the correlation process. CorRelator source code is available at: https://github.com/wright-cemrc-projects/corr.
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Affiliation(s)
- Jie E Yang
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Cryo-Electron Microscopy Research Center, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Midwest Center for Cryo-Electron Tomography, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States
| | - Matthew R Larson
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Cryo-Electron Microscopy Research Center, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Midwest Center for Cryo-Electron Tomography, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States
| | - Bryan S Sibert
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Cryo-Electron Microscopy Research Center, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Midwest Center for Cryo-Electron Tomography, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States
| | - Samantha Shrum
- Biophysics Graduate Program, University of Wisconsin, Madison, WI 53706, United States
| | - Elizabeth R Wright
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Cryo-Electron Microscopy Research Center, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Biophysics Graduate Program, University of Wisconsin, Madison, WI 53706, United States; Morgridge Institute for Research, Madison, WI, 53715, United States; Midwest Center for Cryo-Electron Tomography, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States.
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8
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Radhakrishnan A, Li X, Grushin K, Krishnakumar SS, Liu J, Rothman JE. Symmetrical arrangement of proteins under release-ready vesicles in presynaptic terminals. Proc Natl Acad Sci U S A 2021; 118:e2024029118. [PMID: 33468631 PMCID: PMC7865176 DOI: 10.1073/pnas.2024029118] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Controlled release of neurotransmitters stored in synaptic vesicles (SVs) is a fundamental process that is central to all information processing in the brain. This relies on tight coupling of the SV fusion to action potential-evoked presynaptic Ca2+ influx. This Ca2+-evoked release occurs from a readily releasable pool (RRP) of SVs docked to the plasma membrane (PM). The protein components involved in initial SV docking/tethering and the subsequent priming reactions which make the SV release ready are known. Yet, the supramolecular architecture and sequence of molecular events underlying SV release are unclear. Here, we use cryoelectron tomography analysis in cultured hippocampal neurons to delineate the arrangement of the exocytosis machinery under docked SVs. Under native conditions, we find that vesicles are initially "tethered" to the PM by a variable number of protein densities (∼10 to 20 nm long) with no discernible organization. In contrast, we observe exactly six protein masses, each likely consisting of a single SNAREpin with its bound Synaptotagmins and Complexin, arranged symmetrically connecting the "primed" vesicles to the PM. Our data indicate that the fusion machinery is likely organized into a highly cooperative framework during the priming process which enables rapid SV fusion and neurotransmitter release following Ca2+ influx.
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Affiliation(s)
| | - Xia Li
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06520
- Microbial Sciences Institute, Yale University School of Medicine, New Haven, CT 06520
| | - Kirill Grushin
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | - Shyam S Krishnakumar
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520;
| | - Jun Liu
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06520;
- Microbial Sciences Institute, Yale University School of Medicine, New Haven, CT 06520
| | - James E Rothman
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520;
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9
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Leung MR, Zeev-Ben-Mordehai T. Cryo-electron microscopy of cholinesterases, present and future. J Neurochem 2020; 158:1236-1243. [PMID: 33222205 PMCID: PMC8518539 DOI: 10.1111/jnc.15245] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 10/30/2020] [Accepted: 11/11/2020] [Indexed: 02/06/2023]
Abstract
Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) exist in a variety of oligomeric forms, each with defined cellular and subcellular distributions. Although crystal structures of AChE and BChE have been available for many years, structures of the physiologically relevant ChE tetramer were only recently solved by cryo‐electron microscopy (cryo‐EM) single‐particle analysis. Here, we briefly review how these structures contribute to our understanding of cholinesterase oligomerization, highlighting the advantages of using cryo‐EM to resolve structures of protein assemblies that cannot be expressed recombinantly. We argue that the next frontier in cholinesterase structural biology is to image membrane‐anchored ChE oligomers directly in their native environment—the cell.
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Affiliation(s)
- Miguel Ricardo Leung
- Cryo-Electron Microscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, The Netherlands.,The Division of Structural Biology, Wellcome Centre for Human Genetics, The University of Oxford, Oxford, UK
| | - Tzviya Zeev-Ben-Mordehai
- Cryo-Electron Microscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, The Netherlands.,The Division of Structural Biology, Wellcome Centre for Human Genetics, The University of Oxford, Oxford, UK
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10
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Tenga R, Medalia O. Structure and unique mechanical aspects of nuclear lamin filaments. Curr Opin Struct Biol 2020; 64:152-159. [DOI: 10.1016/j.sbi.2020.06.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2020] [Revised: 06/15/2020] [Accepted: 06/21/2020] [Indexed: 11/15/2022]
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11
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Kamyshinsky RA, Chesnokov YM, Orekhov AS. Cryo-Electron Tomography Studies of Cell Systems. CRYSTALLOGR REP+ 2020. [DOI: 10.1134/s1063774520050090] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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12
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Phillips MA, Harkiolaki M, Susano Pinto DM, Parton RM, Palanca A, Garcia-Moreno M, Kounatidis I, Sedat JW, Stuart DI, Castello A, Booth MJ, Davis I, Dobbie IM. CryoSIM: super-resolution 3D structured illumination cryogenic fluorescence microscopy for correlated ultrastructural imaging. OPTICA 2020; 7:802-812. [PMID: 34277893 PMCID: PMC8262592 DOI: 10.1364/optica.393203] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 05/27/2020] [Accepted: 06/05/2020] [Indexed: 05/19/2023]
Abstract
Rapid cryopreservation of biological specimens is the gold standard for visualizing cellular structures in their true structural context. However, current commercial cryo-fluorescence microscopes are limited to low resolutions. To fill this gap, we have developed cryoSIM, a microscope for 3D super-resolution fluorescence cryo-imaging for correlation with cryo-electron microscopy or cryo-soft X-ray tomography. We provide the full instructions for replicating the instrument mostly from off-the-shelf components and accessible, user-friendly, open-source Python control software. Therefore, cryoSIM democratizes the ability to detect molecules using super-resolution fluorescence imaging of cryopreserved specimens for correlation with their cellular ultrastructure.
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Affiliation(s)
- Michael A. Phillips
- Micron Advanced Bio-imaging Unit, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU,
UK
- STRUBI, Division of Structural Biology, Wellcome Centre for Human Genetics, Old Road Campus, Roosevelt Drive, Oxford OX3 7BN,
UK
- Diamond Light Source, Harwell Science & Innovation Campus, Didcot, Oxfordshire OX11 0DE,
UK
| | - Maria Harkiolaki
- Diamond Light Source, Harwell Science & Innovation Campus, Didcot, Oxfordshire OX11 0DE,
UK
| | - David Miguel Susano Pinto
- Micron Advanced Bio-imaging Unit, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU,
UK
| | - Richard M. Parton
- Micron Advanced Bio-imaging Unit, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU,
UK
| | - Ana Palanca
- Department of Anatomy and Cell Biology, Faculty of Medicine, Universidad de Cantabria, CP39011 Santander,
Spain
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU,
UK
| | - Manuel Garcia-Moreno
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU,
UK
| | - Ilias Kounatidis
- Diamond Light Source, Harwell Science & Innovation Campus, Didcot, Oxfordshire OX11 0DE,
UK
| | - John W. Sedat
- Department of Biochemistry and Biophysics, University of California, San Francisco, California 94143,
USA
| | - David I. Stuart
- STRUBI, Division of Structural Biology, Wellcome Centre for Human Genetics, Old Road Campus, Roosevelt Drive, Oxford OX3 7BN,
UK
- Diamond Light Source, Harwell Science & Innovation Campus, Didcot, Oxfordshire OX11 0DE,
UK
| | - Alfredo Castello
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU,
UK
| | - Martin J. Booth
- Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ,
UK
| | - Ilan Davis
- Micron Advanced Bio-imaging Unit, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU,
UK
- e-mail:
| | - Ian M. Dobbie
- Micron Advanced Bio-imaging Unit, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU,
UK
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13
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Song J, Patterson R, Metlagel Z, Krey JF, Hao S, Wang L, Ng B, Sazzed S, Kovacs J, Wriggers W, He J, Barr-Gillespie PG, Auer M. A cryo-tomography-based volumetric model of the actin core of mouse vestibular hair cell stereocilia lacking plastin 1. J Struct Biol 2020; 210:107461. [PMID: 31962158 PMCID: PMC7067663 DOI: 10.1016/j.jsb.2020.107461] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 01/11/2020] [Accepted: 01/14/2020] [Indexed: 12/11/2022]
Abstract
Electron cryo-tomography allows for high-resolution imaging of stereocilia in their native state. Because their actin filaments have a higher degree of order, we imaged stereocilia from mice lacking the actin crosslinker plastin 1 (PLS1). We found that while stereocilia actin filaments run 13 nm apart in parallel for long distances, there were gaps of significant size that were stochastically distributed throughout the actin core. Actin crosslinkers were distributed through the stereocilium, but did not occupy all possible binding sites. At stereocilia tips, protein density extended beyond actin filaments, especially on the side of the tip where a tip link is expected to anchor. Along the shaft, repeating density was observed that corresponds to actin-to-membrane connectors. In the taper region, most actin filaments terminated near the plasma membrane. The remaining filaments twisted together to make a tighter bundle than was present in the shaft region; the spacing between them decreased from 13 nm to 9 nm, and the apparent filament diameter decreased from 6.4 to 4.8 nm. Our models illustrate detailed features of distinct structural domains that are present within the stereocilium.
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Affiliation(s)
- Junha Song
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Roma Patterson
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Zoltan Metlagel
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Jocelyn F Krey
- Oregon Hearing Research Center & Vollum Institute, Oregon Health & Science University, Portland, OR, USA
| | - Samantha Hao
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Linshanshan Wang
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Brian Ng
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Salim Sazzed
- Department of Computer Science, Old Dominion University, Norfolk, VA, USA
| | - Julio Kovacs
- Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, VA, USA
| | - Willy Wriggers
- Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, VA, USA
| | - Jing He
- Department of Computer Science, Old Dominion University, Norfolk, VA, USA
| | - Peter G Barr-Gillespie
- Oregon Hearing Research Center & Vollum Institute, Oregon Health & Science University, Portland, OR, USA.
| | - Manfred Auer
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
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14
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Srivastava A, Tiwari SP, Miyashita O, Tama F. Integrative/Hybrid Modeling Approaches for Studying Biomolecules. J Mol Biol 2020; 432:2846-2860. [DOI: 10.1016/j.jmb.2020.01.039] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 01/20/2020] [Accepted: 01/24/2020] [Indexed: 12/12/2022]
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15
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Banerjee C, Dutta M, Liu X, Roux KH, Taylor KA. Segmentation by classification: A novel and reliable approach for semi-automatic selection of HIV/SIV envelope spikes. J Struct Biol 2020; 209:107426. [PMID: 31733279 DOI: 10.1016/j.jsb.2019.107426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Revised: 09/28/2019] [Accepted: 11/12/2019] [Indexed: 11/30/2022]
Abstract
We describe a semiautomated approach to segment Env spikes from the membrane envelope of Simian Immunodeficiency Virus visualized by cryoelectron tomography of frozen-hydrated specimens. Multivariate data analysis is applied to a large set of overlapping subvolumes extracted semiautomatically from the viral envelope and does not utilize a template of the target structure. The major manual step used in the method involves determination of six points that define an ellipsoid approximating the virion shape. The approach is robust to departures of the actual virion from this starting ellipsoid. A point cage of sufficient density is generated to ensure that any spike-like protein is identified multiple times. Subsequently translational alignment of class averages to a cylindrical reference on a curved surface separates subvolumes with spikes from those without. Spike containing subvolumes identified multiple times are removed by proximity analysis. Slightly different procedures segment spikes in the equatorial and the polar regions. Once all spikes are segmented, further alignment of class averages using separately the polar and spin angles produces recognizable spike images. Our approach localized 96% of the equatorial spikes and 85% of all spikes identified manually; it identifies a significant number of additional spikes missed by manual selection. Two types of spike shapes were segmented, one with near 3-fold symmetry resembling the conventional spike, the other had a T-shape resembling the spike structure obtained when antibodies such as PG9 bind to HIV Env. The approach should be applicable to segmentation of any protein spikes extending from a cellular or virion envelope.
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Affiliation(s)
- Chaity Banerjee
- Department of Computer Science, Florida State University, Tallahassee, FL 32306-4530, United States.
| | - Moumita Dutta
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, United States.
| | - Xiuwen Liu
- Department of Computer Science, Florida State University, Tallahassee, FL 32306-4530, United States.
| | - Kenneth H Roux
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, United States.
| | - Kenneth A Taylor
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306-4380, United States.
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16
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Engel L, Gaietta G, Dow LP, Swift MF, Pardon G, Volkmann N, Weis WI, Hanein D, Pruitt BL. Extracellular matrix micropatterning technology for whole cell cryogenic electron microscopy studies. JOURNAL OF MICROMECHANICS AND MICROENGINEERING : STRUCTURES, DEVICES, AND SYSTEMS 2019; 29:115018. [PMID: 32879557 PMCID: PMC7457726 DOI: 10.1088/1361-6439/ab419a] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Cryogenic electron tomography is the highest resolution tool available for structural analysis of macromolecular organization inside cells. Micropatterning of extracellular matrix (ECM) proteins is an established in vitro cell culture technique used to control cell shape. Recent traction force microscopy studies have shown correlation between cell morphology and the regulation of force transmission. However, it remains unknown how cells sustain increased strain energy states and localized stresses at the supramolecular level. Here, we report a technology to enable direct observation of mesoscale organization in epithelial cells under morphological modulation, using a maskless protein photopatterning method (PRIMO) to confine cells to ECM micropatterns on electron microscopy substrates. These micropatterned cell culture substrates can be used in mechanobiology research to correlate changes in nanometer-scale organization at cell-cell and cell-ECM contacts to strain energy states and traction stress distribution in the cell.
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Affiliation(s)
- Leeya Engel
- Department of Bioengineering, Stanford University, Stanford, California
- Correspondence:
| | - Guido Gaietta
- Immunity and Pathogenesis Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Liam P. Dow
- Department of Bioengineering, Stanford University, Stanford, California
- Biomolecular Science and Engineering Program, University of California, Santa Barbara
| | - Mark F. Swift
- Immunity and Pathogenesis Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Gaspard Pardon
- Department of Bioengineering, Stanford University, Stanford, California
| | - Niels Volkmann
- Immunity and Pathogenesis Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - William I. Weis
- Departments of Structural Biology and Molecular and Cellular Physiology, Stanford University School of Medicine
| | - Dorit Hanein
- Immunity and Pathogenesis Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Beth L. Pruitt
- Department of Bioengineering, Stanford University, Stanford, California
- Biomolecular Science and Engineering Program, University of California, Santa Barbara
- Departments of Mechanical Engineering and Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara
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17
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Metlagel Z, Krey JF, Song J, Swift MF, Tivol WJ, Dumont RA, Thai J, Chang A, Seifikar H, Volkmann N, Hanein D, Barr-Gillespie PG, Auer M. Electron cryo-tomography of vestibular hair-cell stereocilia. J Struct Biol 2019; 206:149-155. [PMID: 30822456 DOI: 10.1016/j.jsb.2019.02.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Revised: 02/13/2019] [Accepted: 02/17/2019] [Indexed: 11/24/2022]
Abstract
High-resolution imaging of hair-cell stereocilia of the inner ear has contributed substantially to our understanding of auditory and vestibular function. To provide three-dimensional views of the structure of stereocilia cytoskeleton and membranes, we developed a method for rapidly freezing unfixed stereocilia on electron microscopy grids, which allowed subsequent 3D imaging by electron cryo-tomography. Structures of stereocilia tips, shafts, and tapers were revealed, demonstrating that the actin paracrystal was not perfectly ordered. This sample-preparation and imaging procedure will allow for examination of structural features of stereocilia in a near-native state.
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Affiliation(s)
- Zoltan Metlagel
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Jocelyn F Krey
- Oregon Hearing Research Center & Vollum Institute, Oregon Health & Science University, Portland, OR, USA
| | - Junha Song
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Mark F Swift
- Immunity and Pathogenesis Program, Sanford Burnham Prebys Medical Discovery Institute, San Diego, USA
| | - William J Tivol
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Rachel A Dumont
- Oregon Hearing Research Center & Vollum Institute, Oregon Health & Science University, Portland, OR, USA
| | - Jasmine Thai
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Alex Chang
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Helia Seifikar
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Niels Volkmann
- Immunity and Pathogenesis Program, Sanford Burnham Prebys Medical Discovery Institute, San Diego, USA
| | - Dorit Hanein
- Immunity and Pathogenesis Program, Sanford Burnham Prebys Medical Discovery Institute, San Diego, USA
| | - Peter G Barr-Gillespie
- Oregon Hearing Research Center & Vollum Institute, Oregon Health & Science University, Portland, OR, USA
| | - Manfred Auer
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
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18
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Kursula P. Shanks — multidomain molecular scaffolds of the postsynaptic density. Curr Opin Struct Biol 2019; 54:122-128. [DOI: 10.1016/j.sbi.2019.01.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 11/24/2018] [Accepted: 01/22/2019] [Indexed: 10/27/2022]
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19
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Li X, Radhakrishnan A, Grushin K, Kasula R, Chaudhuri A, Gomathinayagam S, Krishnakumar SS, Liu J, Rothman JE. Symmetrical organization of proteins under docked synaptic vesicles. FEBS Lett 2019; 593:144-153. [PMID: 30561792 PMCID: PMC6353562 DOI: 10.1002/1873-3468.13316] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 12/13/2018] [Accepted: 12/17/2018] [Indexed: 11/11/2022]
Abstract
During calcium‐regulated exocytosis, the constitutive fusion machinery is ‘clamped’ in a partially assembled state until synchronously released by calcium. The protein machinery involved in this process is known, but the supra‐molecular architecture and underlying mechanisms are unclear. Here, we use cryo‐electron tomography analysis in nerve growth factor‐differentiated neuro‐endocrine (PC12) cells to delineate the organization of the release machinery under the docked vesicles. We find that exactly six exocytosis modules, each likely consisting of a single SNAREpin with its bound Synaptotagmins, Complexin, and Munc18 proteins, are symmetrically arranged at the vesicle–PM interface. Mutational analysis suggests that the symmetrical organization is templated by circular oligomers of Synaptotagmin. The observed arrangement, including its precise radial positioning, is in‐line with the recently proposed ‘buttressed ring hypothesis’.
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Affiliation(s)
- Xia Li
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT, USA.,Institute of Nautical Medicine, Co-innovation Center of Neuroregeneration, Nantong University, China
| | | | - Kirill Grushin
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Ravikiran Kasula
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Arunima Chaudhuri
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | | | - Shyam S Krishnakumar
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.,Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, UK
| | - Jun Liu
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT, USA.,Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - James E Rothman
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.,Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, UK
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20
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Hinck AP. Structure-guided engineering of TGF-βs for the development of novel inhibitors and probing mechanism. Bioorg Med Chem 2018; 26:5239-5246. [PMID: 30026042 DOI: 10.1016/j.bmc.2018.07.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 06/05/2018] [Accepted: 07/06/2018] [Indexed: 02/07/2023]
Abstract
The increasing availability of detailed structural information on many biological systems provides an avenue for manipulation of these structures, either for probing mechanism or for developing novel therapeutic agents for treating disease. This has been accompanied by the advent of several powerful new methods, such as the ability to incorporate non-natural amino acids or perform fragment screening, increasing the capacity to leverage this new structural information to aid in these pursuits. The abundance of structural information also provides new opportunities for protein engineering, which may become more and more relevant as treatment of diseases using gene therapy approaches become increasingly common. This is illustrated by example with the TGF-β family of proteins, for which there is ample structural information, yet no approved inhibitors for treating diseases, such as cancer and fibrosis that are promoted by excessive TGF-β signaling. The results presented demonstrate that through several relatively simple modifications, primarily involving the removal of an α-helix and replacement of it with a flexible loop, it is possible to alter TGF-βs from being potent signaling proteins into inhibitors of TGF-β signaling. The engineered TGF-βs have improved specificity relative to kinase inhibitors and a much smaller size compared to monoclonal antibodies, and thus may prove successful as either as an injected therapeutic or as a gene therapy-based therapeutic, where other classes of inhibitors have failed.
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Affiliation(s)
- Andrew P Hinck
- Department of Structural Biology, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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21
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Abou-Hamdan A, Belot L, Albertini A, Gaudin Y. Monomeric Intermediates Formed by Vesiculovirus Glycoprotein during Its Low-pH-induced Structural Transition. J Mol Biol 2018; 430:1685-1695. [PMID: 29678555 PMCID: PMC7126088 DOI: 10.1016/j.jmb.2018.04.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 04/06/2018] [Accepted: 04/10/2018] [Indexed: 01/26/2023]
Abstract
•Vesiculovirus G is the prototype of class III viral fusion glycoproteins. •The structures of both G pre- and post-fusion conformation have been determined. •The structure of monomeric intermediates reveals the pathway of the transition. •A fusion-loop-exposing antiparallel dimer may initiate the fusion process. •Those data challenge the current model proposed for viral membrane fusion.
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Affiliation(s)
- Abbas Abou-Hamdan
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - Laura Belot
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - Aurélie Albertini
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - Yves Gaudin
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France.
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